people who try to clearly define musical genres are usually boring mugs not worth listening to anyway.
machine head are an interesting case. they're not a nu-metal band and weren't to begin with but they jumped on the bandwagon for a while at the turn of the century.
obvious differences from their previous work. rapping, extra down-tuning, "personal" lyrics, no guitar solos.
from looking like this:
thankfully they came to their senses and returned to their glory days.